The present invention relates to a power supply apparatus applicable to portable equipment.
Of the many types of portable equipment, a portable bar code reader (handy terminal) has attracted interest. The portable equipment such as the portable bar code reader encases devices such as a CPU the and a memory. This portable bar code reader, as illustrated in FIG. 7, comprises an evenly flat type casing 91 whose tip portion is used as a reading opening 92. Light emitted from a light-emitting diode 93 advances through a condensing lens, formed in a portion of a dust protective plate 94 at the vicinity of the aforementioned opening 92, to a bar code C. The light reflected on the bar code C is incident on an image sensor 96 through a lens 95 within the casing 91 so as to be processed by a CPU (not shown) provided on a printed circuit board 97. After processing by the CPU, necessary information is displayed on a display 98. A plurality of push-buttons are provided on the casing 91, and one of the plurality of push-buttons is used as a power switch 7. The operations of the respective circuits provided in the handy terminal are ensured by a power of a battery 1 disposed within a casing 91. Generally, a Ni--Cd cell is used as the battery 1. This is because an alkaline cell, which is the most commonly used cell, has a problem in that its output voltage gradually decreases from its rated voltage (1.5 V) with use so as to make it difficult to surely keep the voltage constant.
However, although keeping its rated voltage (1.2 V) relatively constant, the Ni--Cd cell has a disadvantage in that the output voltage rapidly decreases when reaching the end of its lifetime, which is generally shorter than that of the alkaline cell. In addition, a special charging device is required for quickly charging the Ni--Cd cell, thus making it difficult to easily use it.